System.out.printf("%.2f", f);

DecimalFormat df = new DecimalFormat("#.##");
result = Double.valueOf(df.format(result));

SimpleDateFormat sdf1 = new SimpleDateFormat("dd/MM/yyyy", Locale.ENGLISH);
String s = "15/04/1990";
Date date = sdf1.parse(s);
SimpleDateFormat sdf2 = new SimpleDateFormat("dd-MMM-yyyy", Locale.ENGLISH);
System.out.println(sdf.format(date));
//output: 15-Apr-1990 (format sdf2)

FileInputStream is = new FileInputStream(fileName);
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String s;
while ((s = br.readLine()) != null) {
       //что-то делаем с s
}

BufferedReader br = new BufferedReader(new FileReader(fileName));
String s;
while ((s = br.readLine()) != null) {
         //что-то делаем с s
}

String.format("The user's name is %s, id = %d", name, id);

ArrayList<Integer> list1 = new ArrayList<Integer>();   //создание списка
Collections.addAll(list1, 1, 5, 6, 11, 3, 15, 7, 8);   //заполнение списка